In Institute of Electrical and Electronics Engineers (IEEE), Wi-Fi, also known as Wireless Local Area Network (WLAN), which terms will be used interchangeably throughout this document, is standardized in the 802.11 specifications such as IEEE Standard for Information technology—Tele-communications and information exchange between systems. Local and metropolitan area networks—Specific requirements. Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications.
Wi-Fi is a technology that currently mainly operates on the 2.4 GHz or the 5 GHz band. The IEEE 802.11 specifications regulate a Station (STA) physical layer, Media Access Control (MAC) layer and other aspects to secure compatibility and inter-operability between access points and portable terminals, here also referred to as UE's. A STA which e.g. may be an access point or a wireless terminal, is a device that has the capability to use the 802.11 protocol. Wi-Fi is generally operated in unlicensed bands. As such, communication over W-Fi may be subject to interference sources from any number of both known and unknown devices. W-Fi is commonly used as wireless extensions to fixed broadband access, e.g., in domestic environments and hotspots, like airports, train stations and restaurants.
Clear Channel Assessment (CCA) Threshold
The WLAN technology relies on Carrier Sensing Multiple Access with Collision Avoidance (CSMA/CA) in order to effectively and fairly share the wireless medium among different WLAN entities and even different Radio Access Technologies (RAT). CSMA/CA applied by the WLAN system demands that every device that wishes to send data senses the common communication channel before carrying a transmission in order to avoid duplicate transmissions, commonly resulting in loss of data and need of retransmissions. In order for a device to deem the channel busy, it has to detect a transmission, the received signal strength level of which surpasses a pre-determined threshold, referred to as the Clear Channel Assessment (CCA) threshold (CCAT). An exemplary relation between the CCAT and the spatial area within which transmitting nodes will cause an Access Point (AP) to defer from transmitting is depicted in FIG. 1. FIG. 1 depicts a scenario where the same CCAT is used regardless of the intended receiver of the upcoming transmission.
The AP will defer from transmitting since the received signal power from nodes within this area is above the CCAT. In current systems one common CCAT is defined for all nodes, to be used when performing channel sensing for transmission to and from any node in the network.
In WLANs, a CCA threshold is specified to define a range within which a WLAN node, e.g. an AP or a STA, will sense the transmission of other WLAN devices to avoid transmission collision. Herein, a WLAN node is node operating in a WLAN such as a WiFi.
Using one or more thresholds based on received power is not optimal from a performance perspective, since nodes in the network may be prevented from transmitting even though the transmission is likely to be successful.